1. Field of the Invention
The present invention relates to methods and apparatus for extracting an enhanced feedstock from vehicular tires by distillation from pyrolysis oil. More specifically, it relates to methods for performing an initial steam separation of the oil which establishes a lighter fraction and a heavier fraction. The lighter fraction may then be subjected to further processing such as by one or more fractional distillations. The lighter fraction can be used as produced or after further separation as a solvent or as a flavoring or scenting agent. The heavier fraction, if desired, may be employed as a solvent, fuel oil, or feedstock for a subsequent chemical process. The heavier fraction may be subjected to removal of polar components including sulfur-containing and nitrogen-containing compounds.
2. Description of the Prior Art
It has been known to subject rubber, such as scrap tires, to pyrolysis with the process producing a solid fraction such as carbon black, a liquid hydrocarbon, and a gas. The liquid hydrocarbon may have potential as a fuel oil. See U.S. Pat. Nos. 6,833,485; 6,835,861; and 7,341,646.
U.S. Pat. No. 4,983,278 discloses a two temperature pyrolysis method which employs oil recycling. It discloses creation of a light oil, heavy oil, and solid residue in a two temperature process.
U.S. Pat. No. 3,702,292 discloses distillation of a crude oil into a number of fractions followed by catalytically cracking a gas oil fraction to form propane and other fractions. U.S. Pat. No. 8,293,952 discloses a pyrolysis process where a basic metal oxide catalyst is employed and a resultant pyrolysis product is said to be high in alcohol content.
It is known that tire-derived pyrolysis oil contains valuable terpenes and other unsaturates as well as mercaptans and other sulfur containing compounds. Attempts to isolate fractions containing these compounds in a commercially viable manner have not been successful. Pyrolysis-derived oil obtained from vehicular tires tend to contain sulfur, nitrogen and oxygen containing compounds. What is derived from pyrolysis of a polymer is a complex mixture of saturated and unsaturated hydrocarbons and includes polar compounds containing sulfur, nitrogen, and oxygen. If desired, subsequent processing may be employed to separate these compounds. Due to the moderate sulfur content of these oils, they are generally used in less environmentally sensitive operations or in those that scrub their emissions to remove sulfur.
It is known that tire-derived pyrolysis oil contains valuable terpenes and other unsaturates as well as benzothiazole and other sulfur-containing compounds. However, attempts to isolate fractions containing these compounds have not yielded commercially valuable fractions. This is due to many issues arising from the complex nature of tire-derived pyrolysis oil. Attempts at direct distillation of the pyrolysis oils yield complex mixtures of compounds and result in instability during distillation. Temperature variation in the heating vessel during the distillation process may cause further instability due to broad boiling point ranges of the constituents. More significantly, pyrolysis oils yield reactive compounds that will react or crack during distillation at the high wall temperatures required by standard distillation, resulting in foaming and difficulty in controlling temperature, pressure, and separation. M. Stanciulescu and M. Ikura (Limonene Ethers from Tire Pyrolysis Oil Part 1: Batch Experiments., J. Analytical and Applied Pyrolysis 75, pp 217-225, 2006.) noted that limonene co-eluted with naphtha and proposed to react the limonene with methanol to shift its boiling point and thereby separate it from the oil. The ester would then be back-reacted. Roy, et. al. (Production of dl-limonene by Vacuum Pyrolysis of Used Tires, J. Analytical and Applied Pyrolysis 57, pp 91-107, 2001.) found that pyrolytic breakdown products of limonene along with thiophene and other sulfur compounds co-eluted with limonene and made clean separation of limonene difficult. This again shows the difficulty in isolating limonene from pyrolysis oil.
U.S. Pat. Nos. 3,871,951; 5,891,501; and 8,329,229 disclose recovery of essential oils and solvents from plant materials by steam distillation. In another process, U.S. Pat. No. 3,197,386 discloses removal of flavorous and odorous substances from oils and fats by steam distillation. In these procedures, plant and animal materials are heated directly in water or steam to vaporize oils and solvents which are then collected by condensation
U.S. Pat. No. 2,662,052 discloses the steam distillation of menthol from mint oil, and plant material and crystalizing the menthol to separate it.
U.S. Pat. No. 5,892,501 discloses the extraction of mint oil from mint plants through steam distillation with the focus of the invention being applying a surfactant on the plant material prior to distillation to resist shattered and lost leaf material as the bulk of the mint oil was said to come from the leaves. The use of the surfactant was said to minimize loss of plant material during processing prior to the steam distillation. This patent does not provide any technical disclosure relevant to applicant's methods.
U.S. Pat. No. 8,329,229 discloses a method for treating the catmint plant in recovery of oils through a multi-stage process which initially employs steam to establish a volatilized mixture of catmint oil and water followed by processing of catmint oil dissolved in water and mixture with the salt also dissolved in the water. It is not directed toward applicant's problem and is not relevant to a solution of the same. See, also, U.S. Pat. No. 3,871,951 which discloses the use of steam distilling to recover turpentine from wood chips while the wood chips are immersed in aqueous alkaline solution.
It is also been known to attempt to isolate terpenes by steam distillation of orange peels and other crop scrap. Such uses present a different problem from the processing of vehicular tire derived pyrolysis oil. However, it would not be obvious to apply this technique to pyrolysis oils.
U.S. Pat. No. 9,920,262 discloses several embodiments of methods of separation of pyrolysis oils. It discloses various combinations which employ two to three phases of the process. Phase I involves a first separation which creates a lighter fraction and a heavier fraction. The lighter fraction is subjected to plate distillation and the heavier fraction is subjected to removal of sulfur and nitrogen compounds in order to facilitate the use of the heavier fraction as heavy fuel oil. A preferred starting material is obtained from vehicular tires. In the initial Phase I portion of the process, thin film distillation is effected in a preferred approach. In a second stage of separation, a lighter fraction emerging from the first separation is subjected to plate distillation. In a third phase, the heavy fraction may be subjected to sulfur and nitrogen removal.
There remains, therefore, a real and substantial need for methods and apparatus for treating pyrolysis oil to effect separation of (a) commercially meaningful fractions from (b) other fractions suitable for use as a solvent, fuel oil, or a feedstock for a subsequent chemical process.